[No QA] ai-reviewer: rules for React's escape hatches by adhorodyski · Pull Request #81651 · Expensify/App

adhorodyski · 2026-02-06T08:39:23Z

@roryabraham @kacper-mikolajczak @mountiny @tgolen

Explanation of Change

This PR adds in new AI reviewer rules as per the predesign wrapped here.

Slack thread with the original rule: https://expensify.slack.com/archives/C05LX9D6E07/p1765986623595829

[PERF-14] Use useSyncExternalStore for external store subscriptions
[PERF-15] Clean up async Effects to prevent race conditions
[PERF-16] Guard initialization logic against double-execution

The original proposal, "Only use React's escape hatches when absolutely necessary", was analyzed against our existing rule set. We found that most of its guidance is already enforced by PERF-6 through PERF-10 (derived state, key resets, event handlers, effect chains, parent communication). What remained were 3 concrete gaps: external store subscriptions, async race conditions, and init double-execution, that couldn't be covered by existing rules.

A meta-rule would have occupied context window budget without producing actionable inline comments, since "absolutely necessary" isn't a mechanically flaggable condition. Instead, these 3 rules close every remaining gap from React's You Might Not Need an Effect guide with precise flag/don't-flag criteria, giving the reviewer clear pass/fail signals rather than philosophical judgment calls.

Fixed Issues

$ #74367
PROPOSAL: https://expensify.slack.com/archives/C05LX9D6E07/p1765986623595829

Tests

Post a PR with offending code and see the reviewer picking it up as something to improve on.

Offline tests

QA Steps

Same as tests.

PR Author Checklist

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

- Suggest useSyncExternalStore for external subscriptions - Warn on async useEffect race conditions without cleanup - Detect unguarded non-idempotent initialization in useEffect with []

melvin-bot · 2026-02-06T08:39:31Z

@ShridharGoel Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

ShridharGoel · 2026-02-06T09:42:15Z

Reviewer Checklist

I have verified the author checklist is complete (all boxes are checked off).
I verified the correct issue is linked in the ### Fixed Issues section above
I verified testing steps are clear and they cover the changes made in this PR
- I verified the steps for local testing are in the Tests section
- I verified the steps for Staging and/or Production testing are in the QA steps section
- I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
- I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
I checked that screenshots or videos are included for tests on all platforms
I included screenshots or videos for tests on all platforms
I verified that the composer does not automatically focus or open the keyboard on mobile unless explicitly intended. This includes checking that returning the app from the background does not unexpectedly open the keyboard.
I verified tests pass on all platforms & I tested again on:
- Android: HybridApp
- Android: mWeb Chrome
- iOS: HybridApp
- iOS: mWeb Safari
- MacOS: Chrome / Safari
If there are any errors in the console that are unrelated to this PR, I either fixed them (preferred) or linked to where I reported them in Slack
I verified there are no new alerts related to the canBeMissing param for useOnyx
I verified proper code patterns were followed (see Reviewing the code)
- I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick).
- I verified that comments were added to code that is not self explanatory
- I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
- I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
- I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
- I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
- I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
- I verified the JSDocs style guidelines (in STYLE.md) were followed
If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
I verified that this PR follows the guidelines as stated in the Review Guidelines
I verified other components that can be impacted by these changes have been tested, and I retested again (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar have been tested & I retested again)
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If a new component is created I verified that:
- A similar component doesn't exist in the codebase
- All props are defined accurately and each prop has a /** comment above it */
- The file is named correctly
- The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
- The only data being stored in the state is data necessary for rendering and nothing else
- For Class Components, any internal methods passed to components event handlers are bound to this properly so there are no scoping issues (i.e. for onClick={this.submit} the method this.submit should be bound to this in the constructor)
- Any internal methods bound to this are necessary to be bound (i.e. avoid this.submit = this.submit.bind(this); if this.submit is never passed to a component event handler like onClick)
- All JSX used for rendering exists in the render method
- The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
If any new file was added I verified that:
- The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
If a new CSS style is added I verified that:
- A similar style doesn't already exist
- The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG)
If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
- I verified that all the inputs inside a form are aligned with each other.
- I added Design label and/or tagged @Expensify/design so the design team can review the changes.
If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
For any bug fix or new feature in this PR, I verified that sufficient unit tests are included to prevent regressions in this flow.
If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
I have checked off every checkbox in the PR reviewer checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

melvin-bot · 2026-02-06T09:42:29Z

We did not find an internal engineer to review this PR, trying to assign a random engineer to #74367 as well as to this PR... Please reach out for help on Slack if no one gets assigned!

Julesssss · 2026-02-06T18:19:32Z

.claude/agents/code-inline-reviewer.md


+### [PERF-14] Use `useSyncExternalStore` for external store subscriptions
+
+- **Search patterns**: `addEventListener`, `subscribe`, `useEffect`, `useState`


This seems quite vague, could we narrow this down at all?

Tried that, but decided to focus on good conditions so it filters out false positives based on more a more nuanced description. I'd leave it as is and improve on as we go if it proves to be too little.

Julesssss · 2026-02-06T18:19:47Z

.claude/agents/code-inline-reviewer.md

+
+- **Condition**: Flag ONLY when ALL of these are true:
+
+  - A `useEffect` subscribes to an external source (DOM events, third-party store, browser API)


Julesssss · 2026-02-06T18:21:17Z

.claude/agents/code-inline-reviewer.md

+
+### [PERF-16] Guard initialization logic against double-execution
+
+- **Search patterns**: `useEffect(`, `}, [])`, `loadData`, `init`, `checkAuth`, `configure`, `setup`, `register`, `start`


Also seems a bit open for false positives. Not sure how this could be improved though

Julesssss

Looking good, it would be great to tighten up some of the search patterns though if possible.

Also could you create a draft PR we can test this workflow against to see if the issues are caught?

roryabraham · 2026-02-06T18:49:33Z

.claude/agents/code-inline-reviewer.md

+}, [query]);
+```
+
+Good (AbortController):


Suggested change

Good (AbortController):

Better (AbortController):

We do all examples though as good/bad, are you sure?

no need to change it 👍🏼

I do think this is slightly better because it kills the request in flight rather than waiting for it to finish. but that's only tangentially related to this rule, so maybe it would only distract from the rule we're trying to enforce.

Add inline reviewer rules for React performance best practices

0de842a

- Suggest useSyncExternalStore for external subscriptions - Warn on async useEffect race conditions without cleanup - Detect unguarded non-idempotent initialization in useEffect with []

adhorodyski requested a review from a team as a code owner February 6, 2026 08:39

melvin-bot bot assigned adhorodyski Feb 6, 2026

melvin-bot bot requested review from ShridharGoel and removed request for a team February 6, 2026 08:39

TMisiukiewicz approved these changes Feb 6, 2026

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ShridharGoel approved these changes Feb 6, 2026

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melvin-bot bot requested a review from Julesssss February 6, 2026 09:42

adhorodyski mentioned this pull request Feb 6, 2026

Convert code-inline-reviewer rules into proactive coding guidelines for Claude #81604

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[No QA] ai-reviewer: rules for React's escape hatches#81651

[No QA] ai-reviewer: rules for React's escape hatches#81651
adhorodyski wants to merge 1 commit intoExpensify:mainfrom
callstack-internal:clean-react-patterns-6

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		### [PERF-14] Use `useSyncExternalStore` for external store subscriptions

		- Search patterns: `addEventListener`, `subscribe`, `useEffect`, `useState`


		- Condition: Flag ONLY when ALL of these are true:

		- A `useEffect` subscribes to an external source (DOM events, third-party store, browser API)


		### [PERF-16] Guard initialization logic against double-execution

		- Search patterns: `useEffect(`, `}, [])`, `loadData`, `init`, `checkAuth`, `configure`, `setup`, `register`, `start`

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adhorodyski commented Feb 6, 2026

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